1. Field of the Invention
The present invention relates to a map data processing apparatus and method for updating map data stored in a map data storing means using the latest map data. The present invention also relates to a map data processing system including the map data processing apparatus.
2. Description of the Related Art
Electronic apparatuses using map data are well known. A typical example of such an apparatus is a vehicle-use navigation system. In a conventional navigation apparatus, map data is stored in a storage medium, such as a CD-ROM, and the entire storage medium is generally exchanged for a new one in order to update the map data stored therein when the use of newer map data is required for accurate navigation.
Meanwhile, a vehicle information system proposal has attracted attention as part of what is known as ITS (Intelligent Transport Systems). In this vehicle information system, various useful information is supplied from an information center to a vehicle via data communication. The offer of the latest map data via communication is also proposed with an expectation such that it may facilitate map data updating.
Japanese Patent Laid-open No. Hei 8-305282 discloses an example of a system in which map data is updated using communication. In this system, an information system has the latest map data, and data communication is carried out between the information center and an on-vehicle navigation apparatus. In the navigation apparatus, map data is stored so as to be read/written in a storing means. For updating the map data stored on the vehicle side, whether or not the stored map data is the latest is determined based on the detected version number. If the data is not the latest version, the latest map data is transmitted from the information center.
The above JP laid-open No. Hei 8-305282 also discloses transmission of differential data from an information center to a vehicle to achieve map data updating in a shorter time. Differential data is data indicative of difference between the latest map data held by the center and older map data held by a vehicle. As differential data has a significantly smaller volume compared to the whole of original map data, it can be transmitted in a shorter time.
In map data updating, it is desirable that processing be completed within the shortest time as possible. Utilizing the above mentioned differential data is one of effective means to increase the update-processing speed. Further, in an updating process, it is important to ensure ease with which updated map data is used in a navigation-related process. That is, it is desirable that an updating process does not result in complicating a process using map data. It is expected that an updating process can be optimized by achieving high-speed update-processing while ensuring ease in using updated map data.
However, at the present stage, map data transmission to a vehicle via communication is still being studied, and none of the conventional technologies takes into consideration compatibility between high-speed update-processing and ease in using updated map data. Therefore, it has been difficult to carry out truly efficient map data updating.
In particular, map data used in a navigation apparatus consists of map data in a number of types. In other words, such total map data is a collection of map data of a number of types. Various map data, such as map data for drawing, for route calculation, and for map matching, may often have different purposes and uses.
In view of high-speed processing and ease in using updated map data, optimum update-processing may differ for every map data. That is, application of similar map data processing may result in significant difference in processing speeds or ease in using map data depending on the type of map data. However, the difference in the nature of respective map data has not conventionally been taken into consideration. As a result, ease in using updated map data may be damaged through application of inappropriate processing.